This invention relates to a method for forming a refractory metal nitride film, and more particularly to a method for forming a refractory metal nitride film having excellent diffusion barrier properties suitable for a dielectric electrode.
A refractory metal nitride film, such as a TiN film or a ZrN film, has been used as a diffusion barrier layer for metals, such as copper, and ferroelectric dielectrics, such as BST(BaSrO.sub.3),
Conventionally, the TiN film or the ZrN film has been deposited using a reactive sputtering method in an excessive N.sub.2 atmosphere. A TiN or ZrN film formed according to this method has a columnar structure having fine grains as shown in FIG. 5B.
The TiN films and the ZrN films formed according to the conventional reactive sputtering method can not act as perfect diffusion barriers due to the formation of pin holes caused by diffusion along the grain boundaries of the films.
Further, the TiN films and the ZrN films formed according to the conventional reactive sputtering method exhibit decreased electrical conductivity due to the substantially great resistivity of the columnar structure, as compared with single crystal TiN or ZrN films.